ULTRASOUND OF THE APPENDIX

 

NORMAL APPENDIX POSITIONS 

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 Refer to this study which concluded that the location of the appendix has wide individual variability,and the limitations of McBurney’s point as an anatomic landmark should be recognized. 

IndicationsFocal RIF pain, Rebound tenderness, Pelvic pain.Elevated WCC (white cell count).

 LIMITATIONS:  Bowel gas and patient habitus are the biggest limiting factors to visualizing the appendix. Up to 60% of appendix’ are retrocaecal and thus may be obscured. Not identifying an appendix does NOT exclude appendicitis. CT Scan is the method of choice for this.

 PREPARATION :The patient should be fasting for 6 hrs only if it is a child. Water in the bladder is an advantage to rule out ovarian pathology in female patients. Unfortunately the appendix is usually an urgent “fit in” and the preparation cannot always be adhered to.

Appendicitis with pain.

Use of a high resolution probe (7-15 MHZ) is essential. Beam steering or compounding can help to overcome anisotropy in linear structures such as tendons. Good colour / power / Doppler capabilities. Be prepared to change frequency output of probe (or probes) to adequately assess both superficial and deeper structures.

Make sure to r/o right  appendix testis torsion.

Or Right ovarian torsion and cyst

 SCANNING TECHNIQUE :  Finding the appendix is highly sonographer dependent. They must have a good skill level to undertake this examination.

 begins by placing the transducer in a transverse position and applying deep graded compression to the displace the gas and bring the bowel closer to the probe.

  • Beginning at the hepatic flexure the bowel is traced down to the cecum.
  • The patient should point to the location of pain .

Lymph nodes can be found with appendicitis and other bowel pathology. 

It is a good idea to have a protocol which includes the entire pelvis of all females with right lower quadrant pain and scanning the renal and biliary systems of all patients with a normal appendix.

Sometimes the external iliac artery and vein can provide a good landmark for finding the appendix because of the location and pulsatility, compressible, and having Doppler flow.

 ULTRASOUND CRITERIA TO DIAGNOSE APPENDICITIS

 In order to demonstrate all the possible presentations of appendicitis it is important that the entire appendix is visualized:

Retro cecal appendicitis can be challenging. 

when the outer diameter of the appendix measures greater than 6 mm

  • Echogenic inflammatory periappendiceal fat change.
  • The wall thickness can measure almost 3 mm or greater

Appendix can be tortuous make sure to find the blind end if you can. 

  • progressed appendicitis can demonstrate a gangrenous appendix. The lumen distends tremendously sometime upwards to 2 cm and is not compressible. An appendicolith may be present which will cast an acoustic shadow. May see hypermia and abscess, fluid fluid and lymph nodes.

Bladder and right lower ureter stones can mimic the appendicitis pain.

  • An appendicolith may be present which will cast an acoustic shadow

 or a perforated appendix is demonstrated when the appendicular wall has ruptured producing fluid or a newly formed abscess. The appearance is hyperechoic with an echo-poor abscess surrounding the appendix. There may be a reflective omentum around the appendix, a thickened bowel, and enlarged lymph nodes. Asymmetrical wall thickening may indicate perforation.

  • Rupture appendix. 

Appendicolith – stones can be seen with posterior shadowing.

  • free fluid in the periappendiceal region

 DIFFERENTIAL DIAGNOSES VISIBLE ON ULTRASOUND

  • Ovarian abnormality , Mesenteric adenitis , Renal calculi

 COMMON PATHOLOGY; Appendicitis ,Mesenteric Adenitis, Ovarian pathology, Crohn’s disease, Diverticulitis, Abscess.

Thank you for reading.

Steve Ramsey, PhD.  MSc- Medical Ultrasound.  Calgary, Alberta, Canada.

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